Nonlinear optical properties of pulsed laser deposited Cu and Zn single and double layer nanostructure thin films

• Nonlinear refractive index in double layer thin films is larger than single layers.
• Nonlinear absorption behaviour in double layer thin films is like that of upper layer.
• Samples with tuneable nonlinear absorption coefficients can be attainable.
• Anomalously, larger nonlinear absorption with larger thickness is obtained.

In this study single and double layer of Cu and Zn nanostructure thin films are prepared by pulse laser deposition technique. The samples are characterized by field emission scanning electron microscopy and optical absorption spectroscopy. The nonlinear refractive index and absorption coefficient of Cu, Zn, Zn/Cu, and Cu/Zn nanostructure thin films are studied by Z-scan method. Zn, Cu/Zn and Zn/Cu nanostructure thin films exhibit positive and Cu nanostructure thin films exhibit negative thermal nonlinear refractive indices, all of the order of 10− 4 cm2/W. Nonlinear absorption coefficient signs of Cu/Zn and Zn nanostructure thin films were positive and those of Zn/Cu and Cu were negative. It is shown that the nonlinear phase shift and the nonlinear refractive index have increased in double layer thin films in comparison with single layer thin films, and also the nonlinear absorption behaviour of double layer thin films is similar to that of the upper layer thin films. Contrary to normal trend, nonlinear absorption coefficient of Cu/Zn double layer thin film has increased in comparison with Zn single layer thin film in spite of increasing thickness. Thus tuneable nonlinear absorption coefficient maybe attainable.